Flat panel systems include controllable display cells, such as liquid crystal display cells, that impart image information onto light transmitted from a light source. The light passes through the display cell to an analyzer (e.g., a polarizer) that resolves the light into a display image that is provided at a display output.
Transmissive display systems include a high-intensity backlight that functions as the light source and cooperates with the display cells to provide a reasonably high brightness display. Such display systems are employed in a variety of electronic devices including, for example, portable personal computers and other computing devices. Such electronic devices in portable operation rely upon a battery power source, and the current draw of a high-intensity backlight imposes a severe limit on the duration of battery-powered portable operation.
Reflective display systems, including high-resolution, multicolor reflective display systems, utilize ambient light to generate display images. No backlight is used. Ambient light received at the viewing surface of a reflective display system passes through a display cell to a reflector, and is reflected back through the display cell to the viewer with an imparted display image. Electronic devices such as portable computers with reflective display systems avoid the battery-powered operating time limitations characteristic of devices with transmissive display systems.
Without a high-intensity backlight, a reflective display system will typically be designed to maximize the amount of ambient light that can be used to maximize the display brightness. In a multicolor display with color filters for generating multiple primary color components (e.g., red, green, and blue), the spectral ranges of light transmitted by each color filter are typically maximized. This can result in significant overlaps in the spectral ranges transmitted by the nominal color filters for the different primary color components.
While improving display brightness, such overlaps in color filter spectral ranges can decrease the accuracy with which colors are rendered by a reflective display system. In particular, overlapping spectral ranges means that pure color components cannot be rendered because of the spectral overlap or “cross-talk” between the color filters. Nevertheless, the improvements in image brightness provided by wide spectrum, overlapping color filters has made such calorimetric inaccuracies an acceptable characteristic of reflective display systems.